Reinforced rubber article



Patented se ezo, 1938 UNITED STATES PATENT OFFICE REINFORCED RUBBERARTICLE John L. Bitter, Johnson City, Tenn., assignor to North AmericanRayon Corporation, New York,

N. Y., a corporation of Delaware 4 Claims.

This is a divisional application of Serial Number 738,690, filed August6, 1934, issued as Patent 2,080,002 on May 11, 1937.

My present invention concerns a new method for preparing threads ofartificial origin which may be employed in the manufacture of automobiletires and the like.

One object of the present invention is to pre-- pare a synthetic threadwhich can be employed to replace the cotton and other threads now in usein the automobile industry, and which will possess characteristicspeculiarly adapting it for such use.

There is between cellulose and rubber somewhat of a naturalincompatibility. The hydroxyl groups of the cellulose and thehydro-carbon structure peculiar to rubber act to repel one anotherrather than to unite. It has been found, however, that carbon in theform of carbon black possesses a natural aflinity for rubber. Inaccordance with my present invention, therefore, I prepare a cellulosicsolution and incorporate with it a quantity of carbon black. Unlikepigments, carbon does not lie inertly in the' solution and in the finalfilaments, but because of its surface activity attracts, to some extent,the cellulose of the solution.

I am well aware that the incorporation of carbon black in a solution,for the purpose of giving it a dull or opaque appearance, has beensuggested. In that case, however, the carbon black was erroneouslyincluded in a group of so-called inorganic pigment-like particles. It isfor its non-pigment-like properties that I am at present 5 making u e ofthis element. It will be especially noted tha the high percentages ofcarbon black employed by me would act to produce an ob- J'ectionablycolored filament when the ordinary use of such yarns is considered.

The exact chemical and physical action of carbon with respect to rubberis not definitely known but several theories have been advancedconcerning thispoi'nt. It is probably best explained by the greatsurface activity of the carbon black particles in co-action with apronounced affinity of carbon for the hydro-carbon characteristics ofthe rubber. I have found that when artificial filaments are prepared inaccordance with my present invention, the carbon embedded in thefilaments possesses a peculiar affinity for the rubber to be employedand thus a closer union of the synthetic thread and the rubber ispossible.

As one way in which my invention may be carried out, the followingexample is given:

I. A viscose solution containing approximately 7% of cellulose is madeup in the ordinary manner and from 10 to 20% of carbon black is dumpedinto the mixer containing the viscose. The percentage is calculated uponthe weight of cellulose present in the solution. This solution is then 5filtered and spun through ordinary spinnerettes. The filaments contain,and have widely dispersed throughout their mass, quantities of thecarbon in finely divided form.

II. As an alternative method, I have found that carbon black may bewetted with sodium hydroxide and may be mixed, or suspended, in aportion of the hydroxide prior to mixing the same with the viscose.

III. In the manufacture of cuprammonium filaments, cellulose is placedin solution in copperoxide-ammonia, and then this solution is spun inthe manner described in Example I above. Similarly, carbon may beincluded in the form of carbon black in nitrocellulosic solutions and insolutions of cellulose esters and others.

My new inventive concept may be also employed with respect to the cottonor other threads now being used in the automobile industry. Cotton maybe coated with a viscose solution prepared, for instance, as set forthin Example I, and this coated thread may be employed in the manufactureof the tire. The mannerin which this may be carried out is clearly setforth in the following example:

IV. A viscose solution is prepared, as set forth in Example I, butinstead of extruding the solution, a cotton thread is passedtherethrough. The carbon impregnated viscose solution forms a coating onthe cotton and this coating is then fixed or precipitated by passing thethread directly into a bath. The threads thus coated may bedesulphurized and dried or otherwise after-treated in the known manner.

It has been found that cotton so treated is more compatible with rubberand thus a natural incompatibility between cellulose and rubber isovercome and a closer union between the treated cotton and the rubber inthe finished product will result.

While I have mentioned the use of from 10-20 of carbon black, it is tobe understood that this proportion gives the best results without undulyweakening filaments to be spun from the solution. If too much carbon isemployed the resulting filaments and the threads made therefrom will belacking pliability and tensile strength. Smaller percentages of carbon,of course, may be employed, but sufiicient should be included to secure5 organic derivatives of cellulose as well.

a good union and co-action between the synthetic material and therubber.

The carbon content of the cellulose solution to be employed when cottonor other natural fiber threads are coated as set forth in Example IVabove, may be varied within greater limits than those just described.This is evident from the fact that the tensile strength of the viscosecoating is not in question and so amounts ranging as high as 50% ofcarbon black, calculated on the weight of the viscose present, may beemployed.

The amount of carbon to be used, of course, depends upon the needsarising in each specific case.

Although Example IV alone is given with respect to viscose, it may beeasily perceived that this process could also be followed with respectto cuprammonium cellulose, cellulose nitrate, and In the cuprammoniumart, for instance, the solution prepared as in Example III above, may beemployed and after passing the cotton therethrough, the

coating could be solidified by using acids or alkalies in .the knownmanner and then the coated filaments could be treated for copperremoval, etc.

Having now set forth my invention as required by the patent statutes,what I claim is:

1. A rubber article having embedded therein strengthening cottonthreads, said threads having a coating of a cellulosic substanceselected from the group consisting of regenerated celiuloses, celluloseesters and cellulose ethers containing about 10 to 50% of a finelydivided carbon black.

2. A rubber article having embedded therein strengthening threads ofcotton, said threads having a coating of a regenerated cellulosecontaining about 10 to 50% of a carbon black.

3. A rubber article having embedded therein strengthening cottonthreads, said threads having a coating of a cellulose ester containingabout 10 to 50% of a finely divided carbon black.

4. A rubber article having embedded therein strengthening cottonthreads, said threads having a coating of a cellulose ether containingabout 10 to 50% of a finely divided carbon black.

JOHN L. BITTER.

